As a sensor capable of detecting a user operation to determine a corresponding operating position with use of a phenomenon in which an electrostatic capacitance of an electrode is varied by the user operation, an electrostatic capacitance type touch pad (hereinafter referred to as an electrostatic pad) is known. The electrostatic pad is a pointing device by which input depending on an operating position is provided, and used for scrolling a screen display and movement of a cursor. The scrolling of a screen display and movement of a cursor are performed by sensing movement of the operating position, and if the electrostatic pad is traced with a finger, a corresponding moving direction is inputted. Such electrostatic pad is easily formed into a thin shape and excellent in durability, as compared with operation keys each including a contact switching type switch in which electrical conduction is made between terminals by pressing, and has therefore conventionally been used in a mobile information terminal as an input device.
In general, a mobile information terminal such as a cellular phone or PDA (Personal Digital Assistants) is required to be portable, and therefore miniaturized. On the other hand, the miniaturization of the electrostatic pad or operation keys in size without reducing operability has a limitation. For this reason, in the mobile information terminal, if the electrostatic pad and the operation keys are attempted to be both arranged, the electrostatic pad and operation keys may be often adjacently arranged, or the electrostatic pad may be often arranged with overlapping with a part of the operation keys. In particular, in the cellular phone often operated with a casing being held by one hand, from the perspective of better operability upon operation by one hand, the electrostatic pad and the operation keys may be often adjacently arranged.